问题
选择题
Mr. Smiths was busy writing a story, only ______ once in a while to smoke a cigarette.
A．to stop
B．to have stopped
C．being stopped
D．stopping
答案
答案：D
题目分析：句意：史密斯先生忙于写故事，只偶尔停下来抽一根烟。Stop和逻辑主语Mr. Smiths 是主谓关系，故用现在分词作伴随状语。故选D。